1. Field of the Invention
The invention generally relates to devices for minimizing work-related injuries caused by the use of computers and particularly to a hand support for use with a computer pointing device such as a computer mouse.
2. Description of Related Art
It is well known that the extended use of a computer pointing device, such as a computer mouse, can cause a computer user to suffer from cumulative trauma disorder (CTD) or repetitive strain injuries (RSI). Computer users can often be afflicted with pains in the hands and the wrists caused by excessive wrist movements such as flexion and hyper-extension of the wrist. Computer users can also suffer from soreness and fatigue in the shoulders and the necks due to excessive arm and shoulder motions associated with use of computer pointing devices.
Long period of repetitive motion associated with the use of the computer mouse coupled with incorrect hand posture while using the mouse may cause disorders in the hand, wrist, elbow, shoulder, and neck, such as carpal tunnel syndrome. Carpal tunnel syndrome is the numbness, tingling and loss of strength of the hand and wrist, and is caused by stress on the wrist induced by repetitive wrist and finger motions. Repetitive stress injuries, such as carpal tunnel syndrome, can be disabling and are costly, both in terms of medical expenses and in terms of lost work time.
The prior art includes several support devices that were used in conjunction with the computer pointing device, such as a computer mouse, to reduce the stress and risk of injury associated with the frequent and repetitive motion necessary in the use of the computer mouse. As described more completely below, typical support devices include stationary or movable apparatus supporting the hand, the wrist or the palm.
U.S. Pat. No. 5,451,020 to Smith et al. and U.S. Pat. No. 5,228,655 to Garcia et al. disclose examples of stationary wrist support devices, also called wrist rests. Wrist rests are typically pads placed in front of the keyboard or the mouse. The height of the pad is selected to support the wrist so as to elevate the hand to be level with the forearm. Wrist rests alleviate the stress on the wrist by avoiding prolonged bending up and down of the wrist.
Stationary wrist rests as those disclosed in Smith et al. and Garcia et al. have a number of disadvantages. Studies have shown that pressure on the underside of the wrist can irritate wrist tissue and increase the risk of carpal tunnel syndrome. Furthermore, wrist rests do not protect the wrist from excessive side to side bending which can cause injuries to the tendons in the wrist. Thus, stationary wrist rests are not a satisfactory means to protect computer users from repetitive stress injuries.
Other types of stationary support devices include the palm rest disclosed in U.S. Pat. No. 5,433,407 to Rice. The stationary palm rest disclosed by Rice involves resting the palm on a raised support where a recess underneath the support permits the mouse to be slid in and under the support. The stationary palm rest disclosed by Rice has several disadvantages. The stationary palm rest raises the hand slightly above the mouse, making it more difficult for the user to control the mouse for fine movements. Typically, a stationary palm rest such as that disclosed by Rice requires the use of only the wrist to move the mouse. The arm and shoulder cannot be effectively used.
Since users often times have limited desktop space, another disadvantage of the stationary wrist rest or palm rest devices disclosed above is that these devices tend to require large amount of desktop space.
U.S. Pat. No. 5,203,845 to Moore discloses a computer mouse support having an upwardly inclined orientation. The mouse support attempts to complement the normal angle of a user's arm during the operation of the mouse. One disadvantage of the mouse support device disclosed by Moore is that the mouse support comprises a wrist/palm support member which can irritate the wrist and injure wrist tissue. As discussed above, a wrist support, that applies pressure to the wrist, is now deemed an invalid way of preventing repetitive stress injuries.
Besides the stationary support devices described above, prior art support devices include movable apparatus. U.S. Pat. No. 5,490,647 to Rice discloses an example of a movable hand support also called a palm rest. Movable palm rests such as that disclosed by the Rice '647 patent tend to fall over easily during use. In addition, existing movable palm rests are particularly inconvenient when the user needs to move between the keyboard and the mouse frequently. Because the movable palm rest tends to be bulky, the user usually cannot locate the palm rest without stopping and visually searching for the device. The need to visually search for the palm rest whenever the user reaches for the mouse and the palm rest is cumbersome and impedes productivity. Also, the movable palm rest such as that disclosed by the Rice '647 patent has other disadvantages. This type of palm rest position the user's hand above the mouse. Because the hand is raised above the mouse with this type of movable palm rests, it is more difficult for the user to control the mouse to make minute and precise mouse movements. Therefore, movable palm rests as those disclosed by the Rice '647 patent are not suitable for users who perform graphics intensive work. Moreover, the height of the movable palm rest makes it difficult for the user to control the mouse with the fingers and the hand; therefore, the user tends to depend on the arm and shoulder to make the mouse movement, much like the device disclosed by U.S. Pat. No. 5,340,067 to Martin et al. that is described more completely below.
U.S. Pat. No. 5,340,067 to Martin et al. discloses a movable hand and wrist support 110 for computer mouse 112 as shown in FIG. 1. Support 110 holds mouse 112 within a retainer 114. The user rests hand 113 on support 110 such that hand 113 is on the same plane as mouse 112.
Movable hand and wrist support 110 that is disclosed by Martin et al. has several disadvantages. First, support 110 has a raised area 116 near the center of support 110 intended to apply gentle pressure on the palm of hand 113. As mentioned previously in reference to palm rests, applying pressure to the center of the palm can cause carpal tunnel syndrome and is highly undesirable. Second, fine mouse movements are made more difficult because the user must move mouse 112 and support together 110. Third, support 110 does not maintain hand 113 in a neutral position because the user has to twist his/her wrist to place hand 113 on the flat surface of support 110.
In addition to the disadvantages described above, prior art support devices are not satisfactory because such devices tend to force the user to focus movement of the user's hand and shoulder in one field of motion only. Stationary palm rests restrict arm and shoulder movement and force the user to move the wrist only in manipulating the mouse. The movable wrist/hand support disclosed by Martin et al. completely eliminates wrist motion, thereby forcing the user to move the arm and shoulder exclusively in manipulating the mouse. Extended and repetitive motions focused on either the wrist or the shoulder can cause cumulative trauma disorders.
Accordingly, there is a need for a support device for use with computer pointing devices, such as a computer mouse, which can reduce stress and helps to prevent injuries while not impeding the productivity of the computer users.